This invention relates to agglomeration and, more particularly, to agglomeration of carbonaceous fines, such as coke fines, bituminous and anthracite coal fines, lignite fines, coal char, lignite char, wood char and the like.
During production, handling and transportation of coke, substantial quantities of fines are generated. Material larger than about 1/4 inch can be used for various applications, such as in charges for steel-making cupolas, blast furnaces and the like. However, smaller fines or breeze are not acceptable for such use and, consequently, usually are either sold at a substantially reduced price for lesser cost-effective uses or disposed of as a waste.
There are substantial quantities of bituminous and anthracite coal fines and lignite fines which presently have limited use because of the difficulty associated with handling, transportation, etc. Non-coking bituminous and anthracite coals and lignite are much more abundant than the special bituminous coal used for making coke. When these materials are heated to an elevated temperature to drive off the volatile ingredients, the resulting char is in a powder-like form instead of the cake-like form of coke and, thus, has limited use. In some countries having limited supplies of coking coal, charred wood is used in place of coke in various processes. Substantial quantities of wood char fines are generated during the charring process and these fines, like the others mentioned above, have limited use.
In order to broaden the applications for these valuable fine materials, there is an apparent need for a process capable of agglomerating them into hardened, crush-resistant pellets, briquettes and similar forms which can be conveniently handled, transported and used for a variety of purposes, including use as part of a charge to steel making processes. Some of these fine materials have been formed into briquettes using asphalt or tar binders and high pressure presses. The resulting briquettes are quite weak and tend to disintegrate during normal handling and transportation. Sintering processes commonly used for producing hardened, crush-resistant mineral agglomerates employ temperatures which are well above the combustion temperature of carbonaceous materials. Low temperature, hydrothermal processes have been used for agglomerating and hardening mineral ores and iron-rich steel plant wastes products which have relatively high inherent strengths. Such processes are exemplified in U.S. Pat. Nos. 3,235,371, 3,770,416 and 3,895,088. However, to the best of applicant's knowledge, this type process has not been used to agglomerate and harden materials containing a major proportion of combustible ingredient(s) having relatively low inherent strengths.